InterNano Nanomanufacturing Repository
Not a member yet
1523 research outputs found
Sort by
Extensional Rheology of Silica Nanoparticles Suspended in AqueousPolyethylene Oxide Solutions
No full textSurface Functionality of Nanoparticles Determines Cellular Uptake Mechanisms in Mammalian Cells
No full textNanoparticles (NPs) are versatile scaffolds for numerous biomedical applications including drug delivery and bioimaging. The surface functionality of NPs essentially dictates intracellular NP uptake and controls their therapeutic action. Using several pharmacological inhibitors, it is demonstrated that the cellular uptake mechanisms of cationic gold NPs in both cancer (HeLa) and normal cells (MCF10A) strongly depend on the NP surface monolayer, and mostly involve caveolae and dynamin-dependent pathways as well as specific cell surface receptors (scavenger receptors). Moreover, these NPs show different uptake mechanisms in cancer and normal cells, providing an opportunity to develop NPs with improved selectivity for delivery applications
Graphene-Supported Pt, Ir, and Pt-Ir Nanoparticles as Electrocatalysts for the Oxidation of Ammonia
No full textGraphene oxide nanosheets are used as a support to anchor metal ions and produce graphene-metal nanoparticle hybrids in a sol-gel method. The influence of experimental conditions on the features of graphene-supported Pt, Ir, and Pt-Ir alloy nanoparticles is studied using transmission electron microscopy. Good dispersion of metal nanoparticles on the graphene sheets are observed for the catalysts heat-treated under exposure to N-2 gas. The existence of metal species with zero oxidation state in the prepared catalysts is evident from the X-ray photoelectron spectroscopy. The characteristic X-ray diffraction peaks of Pt are observed for the graphene-supported Pt and Pt-Ir catalysts. Electrochemical activity of the finely dispersed catalysts toward ammonia oxidation is investigated using cyclic voltammetry. The performance increased in the order Ir < Pt a parts per thousand Pt-Ir
Synchronous chemical vapor deposition of large-area hybrid graphene-carbon nanotube architectures
No full textWe report on the successful synthesis of a graphene-carbon nanotube (CNT) hybrid architecture by a parallel chemical vapor deposition (CVD) of the two carbon allotropes. The carbon hybrid is a three-dimensional (3D) nanostructure with tuneable architecture comprising vertically grown CNTs as pillars and a large-area graphene plane as the floor. The formation of CNTs and graphene occurs simultaneously in a single CVD growth that we describe as a synchronous synthesis method. Unique nature of the fabrication approach contributes significantly to the quality and composure of final nanohybrid. Detailed characterization elucidates the cohesive structure and robust contact between the graphene floor and the CNTs in the hybrid structure. The functionality of the synthesized graphene hybrid structure has been demonstrated by its incorporation into a super-capacitor cell. Our fabrication approach provides an attractive pathway for the fabrication of novel 3D hybrid nanostructures and efficient device integration
Self-Assembly of Gold Nanoparticles on Gallium Droplets: Controlling Charge Transport through Microscopic Devices
No full textWe describe the spontaneous assembly of ligand-stabilized gold nanoparticles on the surfaces of gallium droplets in suspension. By subsequent deposition of these coated droplets onto substrates with patterned electrodes, we form devices that have controlled architecture on the nanometer scale, which allows control of electron transport. In particular, we show that microscopic droplets can be brought into contact with one another with a monolayer of nanopartides between them, resulting in a junction where electron transport is limited by the Coulomb blockade effect. We characterize the gallium surfaces by optical and electron microscopy and measurement of the interfacial tension. We measure the current voltage characteristics of devices consisting of one or more Ga droplets and nanoparticle layers in series. The results agree well with the conventional theory of the Coulomb blockade and show how this approach could be used to form hierarchically structured electronic devices
Directed Assembly of Block Copolymer Templates for the Fabrication of Mesoporous Silica Films with Controlled Architectures via 3-D Replication
No full textMesoporous silica films with cylindrical or spherical pores up to 40 nm in diameter were fabricated by replicating the morphologies of polystyrene-b-poly(tert-butyl acrylate), PS-b-PtBA, copolymers using CO2-assisted infusion and phase selective condensation of tetraethylorthosilicate within the polymer template. The template structures, including domain packing, orientation and spacing were controlled by adjusting the molecular weight, volume fraction and polydispersities of the block copolymers and by solvent annealing. Cylinder alignment was achieved in polymer templates through directed self-assembly (DSA). The structural details imparted to the template prior to precursor infusion were retained in the mesoporous films. In one example, aligned PS-b-PtBA templates were replicated to yield massively parallel arrays of cylindrical pores with pore diameters up to similar to 20 nm. The ability to tune pore sizes in this range within aligned nanochannels is attractive for applications involving biomolecules
Thermally Reversible Aggregation of Gold Nanoparticles in Polymer Nanocomposites through Hydrogen Bonding
No full textThe ability to tune the state of dispersion or aggregation of nanoparticles within polymer-based nanocomposites, through variations in the chemical and physical interactions with the polymer matrix, is desirable for the design of materials with switchable properties. In this study, we introduce a simple and effective means of reversibly controlling the association state of nanoparticles based on the thermal sensitivity of hydrogen bonds between the nanoparticle ligands and the matrix. Strong hydrogen bonding interactions provide excellent dispersion of gold nanoparticles functionalized with poly(styrene-r-2-vinylpyridine) P(S-r-2VP) ligands in a poly(styrene-r-4-vinyl phenol) P(S-r-4VPh) matrix. However, annealing at higher temperatures diminishes the strength of these hydrogen bonds, driving the nanoparticles to aggregate. This behavior is largely reversible upon annealing at reduced temperature with redispersion occurring on a time-scale of similar to 30 min for samples annealed 50 degrees C above the glass transition temperature of the matrix. Using ultraviolet-visible absorption spectroscopy (UV-vis) and transmission electron microscopy (TEM), we have established the reversibility of aggregation and redispersion through multiple cycles of heating and cooling
Nanomanufacturing: path to implementing nanotechnology
No full textResearch and development work in nanoscience and nanotechnology has generated new fundamental understanding of physical phenomena and material behaviour at the nano-scale. This knowledge has resulted in discoveries of new materials, structures and devices. It is believed that these basic research investments should now lead to new products and applications. The general feeling is that nanotechnology needs to move from fundamentals to practice, from the laboratory to the marketplace. The broad consensus is that we need accelerated research and development investments in nanomanufacturing science to step up transition of nanotechnology and to hasten technology transfer. Such an effort will fulfil nanotechnology's promise, which to bring about economic and societal benefits. This paper will define and discuss our perspective on nanomanufacturing, describe our manufacturing science programmes ongoing research and development efforts, list manufacturing challenges and discuss how these are being met through our basic research programmes